cloudflared-mirror/origin/supervisor.go

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package origin
import (
"context"
"fmt"
"net"
"time"
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"github.com/google/uuid"
)
const (
// Waiting time before retrying a failed tunnel connection
tunnelRetryDuration = time.Second * 10
// SRV record resolution TTL
resolveTTL = time.Hour
// Interval between registering new tunnels
registrationInterval = time.Second
)
type Supervisor struct {
config *TunnelConfig
edgeIPs []*net.TCPAddr
// nextUnusedEdgeIP is the index of the next addr k edgeIPs to try
nextUnusedEdgeIP int
lastResolve time.Time
resolverC chan resolveResult
tunnelErrors chan tunnelError
tunnelsConnecting map[int]chan struct{}
// nextConnectedIndex and nextConnectedSignal are used to wait for all
// currently-connecting tunnels to finish connecting so we can reset backoff timer
nextConnectedIndex int
nextConnectedSignal chan struct{}
}
type resolveResult struct {
edgeIPs []*net.TCPAddr
err error
}
type tunnelError struct {
index int
err error
}
func NewSupervisor(config *TunnelConfig) *Supervisor {
return &Supervisor{
config: config,
tunnelErrors: make(chan tunnelError),
tunnelsConnecting: map[int]chan struct{}{},
}
}
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func (s *Supervisor) Run(ctx context.Context, connectedSignal chan struct{}, u uuid.UUID) error {
logger := s.config.Logger
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if err := s.initialize(ctx, connectedSignal, u); err != nil {
return err
}
var tunnelsWaiting []int
backoff := BackoffHandler{MaxRetries: s.config.Retries, BaseTime: tunnelRetryDuration, RetryForever: true}
var backoffTimer <-chan time.Time
tunnelsActive := s.config.HAConnections
for {
select {
// Context cancelled
case <-ctx.Done():
for tunnelsActive > 0 {
<-s.tunnelErrors
tunnelsActive--
}
return nil
// startTunnel returned with error
// (note that this may also be caused by context cancellation)
case tunnelError := <-s.tunnelErrors:
tunnelsActive--
if tunnelError.err != nil {
logger.WithError(tunnelError.err).Warn("Tunnel disconnected due to error")
tunnelsWaiting = append(tunnelsWaiting, tunnelError.index)
s.waitForNextTunnel(tunnelError.index)
if backoffTimer == nil {
backoffTimer = backoff.BackoffTimer()
}
// If the error is a dial error, the problem is likely to be network related
// try another addr before refreshing since we are likely to get back the
// same IPs in the same order. Same problem with duplicate connection error.
if s.unusedIPs() {
s.replaceEdgeIP(tunnelError.index)
} else {
s.refreshEdgeIPs()
}
}
// Backoff was set and its timer expired
case <-backoffTimer:
backoffTimer = nil
for _, index := range tunnelsWaiting {
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go s.startTunnel(ctx, index, s.newConnectedTunnelSignal(index), u)
}
tunnelsActive += len(tunnelsWaiting)
tunnelsWaiting = nil
// Tunnel successfully connected
case <-s.nextConnectedSignal:
if !s.waitForNextTunnel(s.nextConnectedIndex) && len(tunnelsWaiting) == 0 {
// No more tunnels outstanding, clear backoff timer
backoff.SetGracePeriod()
}
// DNS resolution returned
case result := <-s.resolverC:
s.lastResolve = time.Now()
s.resolverC = nil
if result.err == nil {
logger.Debug("Service discovery refresh complete")
s.edgeIPs = result.edgeIPs
} else {
logger.WithError(result.err).Error("Service discovery error")
}
}
}
}
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func (s *Supervisor) initialize(ctx context.Context, connectedSignal chan struct{}, u uuid.UUID) error {
logger := s.config.Logger
edgeIPs, err := ResolveEdgeIPs(s.config.EdgeAddrs)
if err != nil {
logger.Infof("ResolveEdgeIPs err")
return err
}
s.edgeIPs = edgeIPs
if s.config.HAConnections > len(edgeIPs) {
logger.Warnf("You requested %d HA connections but I can give you at most %d.", s.config.HAConnections, len(edgeIPs))
s.config.HAConnections = len(edgeIPs)
}
s.lastResolve = time.Now()
// check entitlement and version too old error before attempting to register more tunnels
s.nextUnusedEdgeIP = s.config.HAConnections
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go s.startFirstTunnel(ctx, connectedSignal, u)
select {
case <-ctx.Done():
<-s.tunnelErrors
// Error can't be nil. A nil error signals that initialization succeed
return fmt.Errorf("context was canceled")
case tunnelError := <-s.tunnelErrors:
return tunnelError.err
case <-connectedSignal:
}
// At least one successful connection, so start the rest
for i := 1; i < s.config.HAConnections; i++ {
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go s.startTunnel(ctx, i, make(chan struct{}), u)
time.Sleep(registrationInterval)
}
return nil
}
// startTunnel starts the first tunnel connection. The resulting error will be sent on
// s.tunnelErrors. It will send a signal via connectedSignal if registration succeed
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func (s *Supervisor) startFirstTunnel(ctx context.Context, connectedSignal chan struct{}, u uuid.UUID) {
err := ServeTunnelLoop(ctx, s.config, s.getEdgeIP(0), 0, connectedSignal, u)
defer func() {
s.tunnelErrors <- tunnelError{index: 0, err: err}
}()
for s.unusedIPs() {
select {
case <-ctx.Done():
return
default:
}
switch err.(type) {
case nil:
return
// try the next address if it was a dialError(network problem) or
// dupConnRegisterTunnelError
case dialError, dupConnRegisterTunnelError:
s.replaceEdgeIP(0)
default:
return
}
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err = ServeTunnelLoop(ctx, s.config, s.getEdgeIP(0), 0, connectedSignal, u)
}
}
// startTunnel starts a new tunnel connection. The resulting error will be sent on
// s.tunnelErrors.
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func (s *Supervisor) startTunnel(ctx context.Context, index int, connectedSignal chan struct{}, u uuid.UUID) {
err := ServeTunnelLoop(ctx, s.config, s.getEdgeIP(index), uint8(index), connectedSignal, u)
s.tunnelErrors <- tunnelError{index: index, err: err}
}
func (s *Supervisor) newConnectedTunnelSignal(index int) chan struct{} {
signal := make(chan struct{})
s.tunnelsConnecting[index] = signal
s.nextConnectedSignal = signal
s.nextConnectedIndex = index
return signal
}
func (s *Supervisor) waitForNextTunnel(index int) bool {
delete(s.tunnelsConnecting, index)
s.nextConnectedSignal = nil
for k, v := range s.tunnelsConnecting {
s.nextConnectedIndex = k
s.nextConnectedSignal = v
return true
}
return false
}
func (s *Supervisor) getEdgeIP(index int) *net.TCPAddr {
return s.edgeIPs[index%len(s.edgeIPs)]
}
func (s *Supervisor) refreshEdgeIPs() {
if s.resolverC != nil {
return
}
if time.Since(s.lastResolve) < resolveTTL {
return
}
s.resolverC = make(chan resolveResult)
go func() {
edgeIPs, err := ResolveEdgeIPs(s.config.EdgeAddrs)
s.resolverC <- resolveResult{edgeIPs: edgeIPs, err: err}
}()
}
func (s *Supervisor) unusedIPs() bool {
return s.nextUnusedEdgeIP < len(s.edgeIPs)
}
func (s *Supervisor) replaceEdgeIP(badIPIndex int) {
s.edgeIPs[badIPIndex] = s.edgeIPs[s.nextUnusedEdgeIP]
s.nextUnusedEdgeIP++
}